Purpose: The study aimed to investigate the use of chitosan alone and combined with organic acids to reduce L. monocytogenes in RTE shrimps during refrigerated storage.
Methods: Cooked RTE shrimps inoculated with L. monocytogenes were dipped for 5 min in 0.5% and 1% (w/v) chitosan solutions and their combinations with 2% acetic acid (v/v), lactic acid (v/v), malic aicd (w/v) or citric acid (w/v), respectively. The treated samples were bagged and stored at 4 °C, and then bacterial counts and color and sensory properties were analyzed for a period of 20 days.
Results: The results indicated that 1% chitosan was more effective than 0.5% chitosan (P < 0.05) to inhibit bacterial growth, and their inhibitory effects were significantly enhanced (P < 0.05) when combined with 2% acetic acid, lactic acid or malic acid, but not citric acid (P > 0.05). The combination of 1% chitosan with 2% acetic acid was the most effective (P < 0.05) and caused 4.42 log CFU/g of bacterial reduction on 20 d when compared with controls, followed by the combined treatment of 1% chitosan with 2% malic acid or 2% lactic acid, respectively. The color and sensory characteristics of shrimps were not adversely affected by different treatment combinations (P > 0.05).
Significance: The study showed that the combined use of chitosan with organic acids could be a promising antimicrobial method to prevent the proliferation of L. monocytogenes in RTE shrimps.